Energy Harvesting, Wireless Structural Health Monitoring System

MicroStrain, Inc. is active in the development of wireless energy harvesting sensors for shipboard & aircraft structural health monitoring (SHM). Recently, flight tests of a Bell M412 helicopter with instrumented pitch links demonstrated that an energy harvester can provide continuous, wireless operational loads tracking of critical rotating structures without battery maintenance. However, not all sensors aboard an aircraft are wireless-"less wire" is often appropriate, particularly when high sample rates and/or power levels may be required. Additional inputs to an integrated SHM system may include the data from engine & control systems, and these data are carried by the vehicle's hard-wired bus. Therefore, there is a need for a scaleable, time-synchronized, sensor network, capable of supporting both wireless & hard-wired sensor networks. Ideally, the system may be tailored to meet the needs of the application. Our objective was to develop & test a versatile, fully programmable SHM system, designed to synchronize & record data from a range of wireless sensors (strain gauges, accelerometers, thermocouples, etc), as well as hard-wired inertial sensors, and data from embedded Global Positioning System (GPS). GPS & inertial sensors (gyroscopes, accelerometers, & magnetometers) provide position, precise timing, & orientation data. Data collected at multiple sampling rates are time stamped & aggregated within a single scaleable database on a base station. The base station processor supports a Linux operating system, secure web interface, eight (8) Gigabytes compact flash memory, CAN, IEEE 802.15.4, Ethernet, RS232/422, GPS, and a GSM cellular modem. Test results for timing performance and system synchronization are presented.